Staying in the Loop

Nelson, his student, John Beausang, and colleagues at Emory University recently reported a new technique to measure rate constants of DNA loop formation and breakdown using tethered particle motion (TPM).

Their technique improves TPM as a quantitative technique with more consistent results and improved time resolution. A typical experimental arrangement, also reported in the article, uses an optically visible bead tethered to a microscope slide (left) using a strand of DNA. The method allows the extraction of DNA-looping events even from very noisy data (right).

The work will appear in the Biophysical Letters section of Biophysical Journal. The technique, a new form of hidden Markov analysis, can provide insight into the physical process of DNA looping and its influence on the biochemistry of transcription.